Circulating ectodysplasin A is a potential biomarker for nonalcoholic fatty liver disease

Ectodysplasin A2 receptor signaling in skeletal muscle pathophysiology

Skeletal muscle is essential in generating mechanical force and regulating energy metabolism and body temperature. Pathologies associated with muscle tissue often lead to impaired physical activity and imbalanced metabolism. Recently, ectodysplasin A2 receptor (EDA2R) signaling has been shown to promote muscle loss and glucose intolerance. Upregulated EDA2R expression in muscle tissue was associated with aging, denervation, cancer cachexia, and muscular dystrophies. Here, we describe the roles of EDA2R signaling in muscle pathophysiology, including muscle atrophy, insulin resistance, and aging-related sarcopenia. We also discuss the EDA2R pathway, which involves EDA-A2 as the ligand and nuclear factor (NF)κB-inducing kinase (NIK) as a downstream mediator, and the therapeutic potential of targeting these proteins in the treatment of muscle wasting and metabolic dysfunction.

Mediterranean Diet Improves Plasma Biomarkers Related to Oxidative Stress and Inflammatory Process in Patients with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) shows liver fat depots without alcohol consumption. NAFLD does not have specific drug therapies, with a healthy lifestyle and weight loss being the main approaches to prevent and treat NAFLD. The aim was to assess the antioxidant and pro-inflammatory state in patients with NAFLD after 12-month-lifestyle intervention depending on the change in adherence to a Mediterranean diet (AMD). Antioxidant and inflammatory biomarkers were measured in 67 adults (aged 40–60 years old) diagnosed with NAFLD. Anthropometric parameters and dietary intake were measured by a validated semi-quantitative 143-item food frequency questionnaire. The nutritional intervention improved anthropometric and biochemical parameters after a 12-month follow-up. However, decreases in alanine aminotransferase (ALT) and C reactive protein (CRP) were higher in participants with high AMD, which also showed higher improvement in physical fitness (Chester step test) and intrahepatic fat contents. The intervention reduced plasma levels of malondialdehyde, myeloperoxidase, zonulin, and omentin, and increased resolvin D1 (RvD1), whereas the decrease in leptin, ectodysplasin-A (EDA), cytokeratin-18 (CK-18), interleukin-1ra (IL-1ra) and endotoxin was only significant in participants with higher AMD. The current study showed that a one-year nutritional intervention improved main NAFLD features such as body mass index, IFC, liver enzymes, and prooxidant and proinflammatory status. There was also a decrease in the concentration of plasmatic endotoxin, suggesting an improvement in intestinal permeability. These health benefits were more evident in participants that improved AMD to a greater extent. The trial was registered at ClinicalTrials.gov with registry number NCT04442620.

Regulatory network and interplay of hepatokines, stellakines, myokines and adipokines in nonalcoholic fatty liver diseases and nonalcoholic steatohepatitis

Fatty liver disease is a spectrum of liver pathologies ranging from simple hepatic steatosis to non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), and culminating with the development of cirrhosis or hepatocellular carcinoma (HCC). The pathogenesis of NAFLD is complex and diverse, and there is a lack of effective treatment measures. In this review, we address hepatokines identified in the pathogenesis of NAFLD and NASH, including the signaling of FXR/RXR, PPARα/RXRα, adipogenesis, hepatic stellate cell activation/liver fibrosis, AMPK/NF-κB, and type 2 diabetes. We also highlight the interaction between hepatokines, and cytokines or peptides secreted from muscle (myokines), adipose tissue (adipokines), and hepatic stellate cells (stellakines) in response to certain nutritional and physical activity. Cytokines exert autocrine, paracrine, or endocrine effects on the pathogenesis of NAFLD and NASH. Characterizing signaling pathways and crosstalk amongst muscle, adipose tissue, hepatic stellate cells and other liver cells will enhance our understanding of interorgan communication and potentially serve to accelerate the development of treatments for NAFLD and NASH.

HPS protects the liver against steatosis, cell death, inflammation, and fibrosis in mice with steatohepatitis

Hepassocin (HPS) is a hepatokine associated with metabolic regulation and development of non-alcoholic steatohepatitis (NASH). However, previous reports on HPS are controversial and its true function is not yet understood. Here, we demonstrated that hepatic HPS expression levels were upregulated in short-term feeding and downregulated in long-term feeding in high-fat diet (HFD)- and methionine- and choline-deficient (MCD) diet-fed mice, as well as in genetically obese (ob/ob) mice. HFD- and MCD-induced hepatic steatosis, inflammation, apoptosis, and fibrosis were more pronounced in HPS knockout mice than in the wild-type mice. Moreover, HPS depletion aggravated HFD-induced insulin resistance. By contrast, HPS administration improved MCD- or HFD-induced liver phenotypes and insulin resistance in HPS knockout and wild-type mice. Mechanistic studies revealed that MCD-induced hepatic oxidative stress was significantly increased by HPS deficiency and could be attenuated by HPS administration. Furthermore, palmitic acid-induced lipid accumulation and oxidative stress were exclusively enhanced in HPS knockout hepatocytes and diminished by HPS cotreatment. These data suggest that HPS ameliorates NASH in mice, at least in part, by inhibiting the oxidative stress. HPS expression levels are downregulated in human fatty liver tissues, suggesting that it may play an important protective role in NASH. Collectively, our findings provide clear genetic evidence that HPS has beneficial effects on the development of steatohepatitis in mice and suggest that upregulating HPS signaling may represent an effective treatment strategy for NASH.

Ectodysplasin A (EDA) Signaling: From Skin Appendage to Multiple Diseases

Ectodysplasin A (EDA) signaling is initially identified as morphogenic signaling regulating the formation of skin appendages including teeth, hair follicles, exocrine glands in mammals, feathers in birds and scales in fish. Gene mutation in EDA signaling causes hypohidrotic ectodermal dysplasia (HED), a congenital hereditary disease with malformation of skin appendages. Interestingly, emerging evidence suggests that EDA and its receptors can modulate the proliferation, apoptosis, differentiation and migration of cancer cells, and thus may regulate tumorigenesis and cancer progression. More recently, as a newly discovered hepatocyte factor, EDA pathway has been demonstrated to be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and type II diabetes by regulating glucose and lipid metabolism. In this review, we summarize the function of EDA signaling from skin appendage development to multiple other diseases, and discuss the clinical application of recombinant EDA protein as well as other potential targets for disease intervention.

Ectodysplasin A/Ectodysplasin A Receptor System and Their Roles in Multiple Diseases

Ectodysplasin A (EDA) is a member of the tumor necrosis factor (TNF) family of ligands that was initially reported to induce the formation of various ectodermal derivatives during normal prenatal development. EDA exerts its biological activity as two splice variants, namely, EDA-A1 and EDA-A2. The former binds to the EDA receptor (EDAR), resulting in the recruitment of the intracellular EDAR-associated death domain (EDARADD) adapter protein and the activation of the NF-κB signaling pathway, while the latter binds to a different receptor, EDA2R, also known as X-linked ectodermal dysplasia receptor (XEDAR). Inactivation mutation of the EDA gene or the genes coding for its receptors can result in hypohidrosis ectodermal dysplasia (HED), a condition that is characterized by oligotrichosis, edentulosis or oligodontia, and oligohidrosis or anhidrosis. Recently, as a new liver factor, EDA is gradually known and endowed with some new functions. EDA levels were observed to be upregulated in several metabolic diseases, such as non-alcoholic fatty liver disease (NAFLD), obesity, and insulin resistance. In addition, EDA and its receptors have been implicated in tumor pathogenesis through the regulation of tumor cell proliferation, apoptosis, differentiation, and migration. Here, we first review the role of EDA and its two-receptor system in various signaling pathways and then discuss the physiological and pathological roles of EDA and its receptors.

Association of EDARV370A with breast density and metabolic syndrome in Latinos

The ectodysplasin receptor (EDAR) is a tumor necrosis factor receptor (TNF) superfamily member. A substitution in an exon of EDAR at position 370 (EDARV370A) creates a gain of function mutant present at high frequencies in Asian and Indigenous American populations but absent in others. Its frequency is intermediate in populations of Mexican ancestry. EDAR regulates the development of ectodermal tissues, including mammary ducts. Obesity and type 2 diabetes mellitus are prevalent in people with Indigenous and Latino ancestry. Latino patients also have altered prevalence and presentation of breast cancer. It is unknown whether EDARV370A might connect these phenomena. The goals of this study were to determine 1) whether EDARV370A is associated with metabolic phenotypes and 2) if there is altered breast anatomy in women carrying EDARV370A. Participants were from two Latino cohorts, the Arizona Insulin Resistance (AIR) registry and Sangre por Salud (SPS) biobank. The frequency of EDARV370A was 47% in the Latino cohorts. In the AIR registry, carriers of EDARV370A (GG homozygous) had significantly (p < 0.05) higher plasma triglycerides, VLDL, ALT, 2-hour post-challenge glucose, and a higher prevalence of prediabetes/diabetes. In a subset of the AIR registry, serum levels of ectodysplasin A2 (EDA-A2) also were associated with HbA1c and prediabetes (p < 0.05). For the SPS biobank, participants that were carriers of EDARV370A had lower breast density and higher HbA1c (both p < 0.05). The significant associations with measures of glycemia remained when the cohorts were combined. We conclude that EDARV370A is associated with characteristics of the metabolic syndrome and breast density in Latinos.

Increased Circulating Levels of Ectodysplasin A in Newly Diagnosed Type 2 Diabetic Patients

OBJECTIVE

Ectodysplasin A (EDA), a newly discovered hepatokine, has recently been considered to be closely related to glycolipid metabolism disorders, but the pathophysiological effects of EDA are still poorly understood. This study was the first time to determine the level of serum EDA in newly diagnosed type 2 diabetes mellitus (T2DM) patients, and to explore the relationships between serum EDA levels and various metabolic indexes.

METHODS

A total of 184 subjects were enrolled in the study, including 92 subjects with newly diagnosed T2DM and 92 subjects with age- and sex-matched normal glucose tolerance (NGT). Serum EDA levels were determined using enzyme-linked immunosorbent assay (ELISA). Oral glucose tolerance test, glycosylated hemoglobin c (HbA1c), and insulin were also measured.

RESULTS

Serum EDA levels were significantly increased in the T2DM group than in the NGT group (359.91 ± 117.99 vs. 265.82 ± 86.51 pg/ml, p < 0.001). Serum EDA levels were positively correlated with body mass index (BMI), waist-to-hip ratio (WHR), fasting plasma glucose (FPG), HbA1c, 2-hour postprandial plasma glucose (2hPG), fasting plasma insulin (FIns), fasting C peptide (FCP), triglyceride (TG), HOMA-IR, and negatively correlated with high-density lipoprotein cholesterol (HDL-c) and HOMA-β (p < 0.05). Multiple stepwise regression analysis demonstrated that 2hPG and FIns were independent influencing factors of serum EDA level (p < 0.05). Logistic regression analysis showed that serum EDA level was significantly independently correlated with T2DM (p < 0.05).

CONCLUSIONS

Serum EDA levels are significantly higher in T2DM patients, suggesting that EDA may play a role in the occurrence and development of T2DM.

Ectodysplasin A Is Increased in Non-Alcoholic Fatty Liver Disease, But Is Not Associated With Type 2 Diabetes

Ectodysplasin A (EDA) was recently identified as a liver-secreted protein that is increased in the liver and plasma of obese mice and causes skeletal muscle insulin resistance. We assessed if liver and plasma EDA is associated with worsening non-alcoholic fatty liver disease (NAFLD) in obese patients and evaluated plasma EDA as a biomarker for NAFLD. Using a cross-sectional study in a public hospital, patients with a body mass index >30 kg/m² (n=152) underwent liver biopsy for histopathology assessment and fasting liver EDA mRNA. Fasting plasma EDA levels were also assessed. Non-alcoholic fatty liver (NAFL) was defined as >5% hepatic steatosis and nonalcoholic steatohepatitis (NASH) as NAFLD activity score ≥3. Patients were divided into three groups: No NAFLD (n=45); NAFL (n=65); and NASH (n=42). Liver EDA mRNA was increased in patients with NASH compared with No NAFLD (P=0.05), but not NAFL. Plasma EDA levels were increased in NAFL and NASH compared with No NAFLD (P=0.03). Plasma EDA was related to worsening steatosis (P=0.02) and fibrosis (P=0.04), but not inflammation or hepatocellular ballooning. ROC analysis indicates that plasma EDA is not a reliable biomarker for NAFL or NASH. Plasma EDA was not increased in patients with type 2 diabetes and did not correlate with insulin resistance. Together, we show that plasma EDA is increased in NAFL and NASH, is related to worsening steatosis and fibrosis but is not a reliable biomarker for NASH. Circulating EDA is not associated with insulin resistance in human obesity.

CLINICAL TRIAL REGISTRATION

https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12615000875505, identifier ACTRN12615000875505.

Liver Expressed Antimicrobial Peptide 2 is Associated with Steatosis in Mice and Humans

BACKGROUND AND AIMS

Liver expressed antimicrobial peptide 2 (LEAP2) is recently identified as a regulator in energy metabolism. This study aims to 1) investigate the role of leap2 in hepatic steatosis in C57BL/6 mice; 2) evaluate the association between circulating LEAP2 levels and liver fat contents in a hospital based case-control study.

METHODS

The rodent experiment: western blotting and qPCR were performed to evaluate leap2 levels, lipid metabolism pathways and insulin signaling. shRNA was used to knockdown leap2. The clinical study: commercial ELISA kits were used to measure circulating LEAP2 levels (validated by western blotting). Liver fat content was estimated using MRI-derived proton density fat fraction and FibroScan-derived controlled attenuation parameter.

RESULTS

The rodent experiment found the hepatic expression and secreted levels of leap2 were increased in mice with diet-induced steatosis. Leap2 knockdown ameliorated steatosis via lipolytic/lipogenic pathway and improved insulin sensitivity via IRS/AKT signaling. The clinical study reported increased circulating levels of LEAP2 in the subjects with steatosis. Moreover, LEAP2 correlated positively with age, body mass index, waist-to-hip ratio, liver fat content, fasting insulin and HOMA-IR, whereas inversely with acyl-ghrelin. Furthermore, the circulating levels of LEAP2 are dependent on liver fat content, acyl-ghrelin and fasting glucose. Lastly, circulating LEAP2 is an independent predictor of NAFLD.

CONCLUSIONS

The study suggests LEAP2 is associated with hepatic steatosis, which may involve lipolytic/lipogenic pathway and insulin signaling.